Arizona Sen. Kyrsten Sinema announced Friday she is leaving the Democratic Party and registering as an independent. The move does not change Senate math in the immediate term, as Sinema will continue to caucus with Democrats, keeping the 51-member majority intact. However, political analysts say her decision significantly complicates the electoral landscape heading into the 2024 Senate cycle.
Sinema's departure follows years of rocky relations between the Arizona senator and her former party. On votes where at least half of Democrats voted differently than half of Republicans from 2013 to 2020, Sinema aligned with her party just 69% of the time — compared to a 90% average for Senate Democrats. The senator was frequently mentioned alongside West Virginia's Joe Manchin as a holdout on key legislation during the Biden administration's first two years.
What the Left Is Saying
Senate Majority Leader Chuck Schumer said in a statement that Sinema informed him of her decision and will continue caucusing with Democrats, preserving the current 51-49 majority structure. "I value our relationship and look forward to continuing to work together for Arizona," he wrote.
Progressive groups were less measured. The Progressive Change Campaign Committee called Sinema's move a "betrayal" of Democratic voters who helped elect her. Rep. Ruben Gallego, who has been mentioned as a potential primary challenger, declined to comment on whether he would still run but noted the party needed strong candidates in purple states like Arizona.
Arizona Democratic Party Chair Yolanda Beavers issued a statement saying Sinema had "turned her back on the grassroots movement that elected her." The state party did not indicate whether it would recruit an alternative candidate. Some Democrats worry privately that without a nominee, Republicans could win the seat if Sinema runs competitively as an independent and splits the non-Republican vote.
What the Right Is Saying
National Republican Senatorial Committee spokesperson Emma Loganguardo said in a statement: "This is pure chaos for Senate Democrats who can barely keep their own party together. Kyrsten Sinema's low approval ratings and her history of bucking both parties make this seat a true wildcard heading into 2024."
Arizona Republicans have not yet announced a Senate candidate for 2024, but the state party's chair, David Shafer, called on Sinema to resign from her committee assignments. "If she no longer represents Democrats, she shouldn't hold Democratic committee seats," Shafer wrote on social media.
Conservative commentator Ben Shapiro argued on his program that Sinema's move could benefit Republicans if it splits moderate and progressive voters in a state Trump carried twice. "Arizona is purple at best for Democrats now," Shapiro said. "Any fracture in the Democratic coalition creates an opening."
What the Numbers Show
Sinema's polling numbers have been persistently weak heading into her 2024 cycle. An autumn 2022 CES poll showed her approval rating among Arizona Democrats at just 25%, with an overall favorability of 25% approve and 58% disapprove — one of the worst marks for any sitting senator in either party.
The historical parallel most cited by analysts is Joe Lieberman, who won a 2006 Connecticut Senate race as an independent after losing the Democratic primary. After that shift, Lieberman's voting alignment with Democrats dropped roughly 10 percentage points compared to his final term as a Democrat — suggesting Sinema could become even more conservative without party primaries to worry about.
For the broader 2024 map: of the 34 Senate seats up for election, 23 are currently held by Democratic-caucusing members. Democrats can retain their majority if they lose no more than one seat assuming they win the presidency (giving them a tie-breaking vice president). Seven of those vulnerable Democratic seats represent states Donald Trump won at least once — including Arizona.
The Bottom Line
Sinema's decision transforms what was already a challenging Senate map into a genuinely uncertain situation for Democrats. While her commitment to caucus with Democrats protects the current majority, it does nothing to guarantee the seat stays in party hands after 2024. Whether the party runs a candidate against her — risking a Charlie Crist-style vote split that handed Florida to Marco Rubio in 2010 — remains undecided.
What happens next will likely depend on Sinema's polling through 2023 and whether high-profile Democrats like Gallego decide the risk of splitting the non-Republican vote outweighs the benefit of an open primary. Republicans, meanwhile, must decide whether to nominate a mainstream candidate who can win in a purple state or risk repeating their 2022 losses by going too far right. The Arizona race is shaping up as one of the most watched Senate contests of the 2024 cycle.